Can't turn off text-to-speech. Other weirdness

I tried text-to-speech yesterday for the first time. After sampling every single voice, I discovered that now I can't turn it off. Since there's no on/off check box, I assume that you turn it off merely by unchecking all three boxes ("Announce when ...", "Announce when ...", and "Speak selected ..."). However, even when they're all unchecked, it still speaks. And it now always speaks in the same (male) voice, regardless of which voice I pick. I can turn the volume down, of course, but since I mostly use the computer for music, that's not an option. Besides, anything which isn't working right worries me!

At the same time, some other new behavior started, even though I haven't made any changes at all in System Preferences:

(1) There are now several new sounds when windows open and close.

(2) Selected items, such as icons, now have heavy rectangles around them.

(3) Sometimes one of those rectangles stays frozen in place on the screen, even when the item it originally surrounded has been scrolled or moved elsewhere.

(4) Sometimes when I click on System Preference | Speech, I get Universal Access instead.

(5) There are now new items in the Apple menu: Besides "Force Quit ...", "Restart ...", "Shut down ...", and "Log out <my name> ..." with ellipsis, which ask me to confirm, there are now the same items without ellipsis which act immediately.

Except for (3) and (4), none of these are "bad". But I still wonder where they suddenly came from.

I have rebooted many times. What else should I try? And what causes all this?